Magnetic heads of the floating type heretofore known for use with hard discs for recording or reproducing signals basically have the same construction as the magnetic head shown in FIG. 1 and to be produced by the process of the invention. The conventional magnetic head comprises a head core 1 having a magnetic gap portion 16, and a slider 2 of nonmagnetic ceramics. The head core 1 is fitted in a core accommodating groove 22 formed in the slider 2 and secured to the slider 2 by being bonded by a glass filled portion 15. As will be described later, the head core 1 is primarily made of a highly magnetic oxide, such as Mn-Zn ferrite. As seen in FIG. 2, the slider 2 having the head core 1 is formed with a pair of parallel faces 21, 21 to be opposed to a magnetic disc 3 and extending in the direction of rotation of the disc 3, with a recess 26 formed between the faces 21, 21. When the magnetic disc 3 is rotated at a high speed in the direction of arrow A, a layer of stable air current is formed between the magnetic disc 3 and the medium opposed faces 21, whereby the magnetic head is held in a floating position relative to the disc surface as specified.
As disclosed in Unexamined Japanese Publication SHO Pat. No. 62-103808, the floating-type magnetic head described is produced by the process illustrated in FIGS. 19 and 20. FIG. 19 shows a core chip 9 and a slider chip 23 which are first prepared separately. The core chip 9 comprises a pair of ferrite core segments 95, 96, with a magnetic gap portion 94 formed at a butt joint therebetween. The core chip 9 has a pair of track width defining grooves 92, 92 at opposite sides of the gap portion 94, whereby a medium opposed portion 93 is formed.
The slider chip 23 is formed, on the surface thereof to be opposed to the magnetic disc, with a pair of projections 24, 25 extending along the direction of rotation of the disc, with a recess 26 provided therebetween. The slider chip 23 has in its front portion a cutout 27 extending radially of the disc, and the above-mentioned core accommodating groove 22 extending perpendicular to the disc.
With reference to FIG. 20, the core chip 9 is then fitted into the groove 22 of the slider chip 23, and a glass rod 91 is placed on the head portion of the core chip 9. The assembly is heated in an oven to melt the glass rod 91, whereupon the molten glass flows into the clearance in the groove 22 around the core chip 9, consequently joining the core chip 9 to the slider chip 23. The projections 24, 25 are thereafter ground to a depth indicated in the broken line F in FIG. 20 and chamfered as required, whereby the same magnetic head as shown in FIG. 1 is completed.
On the other hand, in securing the core chip 9 to the slider chip 23 by melting glass, a method has been proposed which is characterized, as shown in FIG. 21, by placing glass rods 97, 97 of high softening point temperature in the respective track width defining grooves 92, 92 of the core chip 9, placing a glass rod 98 of low softening point temperature on the medium opposed portion 93, and melting at least the glass rod 98 of low softening point temperature (see Unexamined Japanese Publication SHO Pat. No. 62-189617).
In this case, the molten glass of low softening point temperature, which is highly flowable, penetrates into the clearances between the slider chip 23 and the core chip 9, and the grooves 92 and the space thereabove are filled up with the glass rods 97 of high softening point temperature and the molten glass. After the molten glass has solidified, the assembly is ground to a level indicated by the broken line G in FIG. 21 to form a medium opposed face 99 as seen in FIG. 22.
The methods shown in FIGS. 21 and 22 produce no voids in the glass filled portion between the core chip 9 and the slider chip 23, so that the head core can be firmly bonded to the slider.
However, when the core chip 9 is inserted into the groove 22 in the slider chip 23 by the conventional method as seen in FIG. 19, the medium opposed portion 93, which has a very small width (e.g., 10 to 30 micrometers) equal to the track width, of the core chip 9 is likely to collide with the slider chip 23 or the like and chip or crack at its end portion to result in a reduced yield.
Furthermore, the glass rods 91, 97 and 98 shown in FIG. 20 or 21 are as small as about 0.5 mm in diameter and are therefore difficult not only to make but also to place on the core chip or in the grooves 22, hence a poor work efficiency. With the magnetic head fabricated by the method shown in FIGS. 21 and 22, the medium opposed face 99 has greatly exposed glass portions 100 high softening point temperature, which therefore afford improved weather resistance, for example, higher moisture resistance. Nevertheless, glass portions 101 of low softening point temperature inevitably become exposed slightly, so that grinding of the medium opposed face 99 involves the problem of creating a step in this face owing to the difference in workability between the glass of low softening point temperature and the glass of high softening point temperature.